The invention relates to a fuel injection system for mixture compressing, spark plug ignited internal combustion engines employing continuous injection into the induction manifold, in which an air-flow measuring element and an arbitrairly actuatable butterfly valve are disposed in sequence. The air-flow measuring element is displaced corresponding to the air flow through the induction tube and against a resetting force produced by pressurized fluid and thereby moves the movable member of a valve assembly disposed within the fuel line for the purpose of metering out a fuel quantity proportional to the air quantity. The metering process occurs at a constant pressure difference.
Fuel injection systems of this type serve the purpose of automatically creating a favorable fuel-air mixture for all operational conditions of the internal combustion engine in order to make possible a complete combustion of the fuel and thus to avoid or at least to reduce sharply the production of toxic exhaust components while maintaining the highest possible performance of the internal combustion engine or the least possible fuel consumption. For this reason, the fuel quantity must be metered out very precisely according to the requirements of each operational state of the internal combustion engine and the proportionality between the air quantity and the fuel quantity must be changed in dependence on motor parameters, e.g. r.p.m., load, temperature and exhaust gas composition. The laws and regulations affecting the permissible exhaust gas constituents of vehicle engines are becoming more severe all the time and make necessary a very precise control of the optimum injected fuel quantity.